[Dr Ali Shirsavar] drawing schematics and equations on the whiteboard

Calculating The Capacitance And ESR Specifications For The Output Capacitor In Your Switching-Mode Power Supply

January 18, 2026 by No comments

[Dr Ali Shirsavar] from Biricha Digital runs us through How to Select the Perfect Output Capacitor for Your Power Supply. Your switching-mode power supply (SMPS) will require an output capacitor both to iron out voltage swings due to loading and to attenuate ripple caused by switching. In this video we learn how to calculate the required capacitance, and when necessary the ESR, for your output capacitor.

To begin [Dr Ali] shows us that in order to calculate the minimum capacitance to mitigate voltage swings we need values for Δi, Δv, and Ts. Using these we can calculate the minimum output capacitance. We then need to calculate another minimum capacitance for our circuit given that we need to attenuate ripple. To calculate this second minimum we need to change our approach depending on the type of capacitor we are using, such as ceramic, or electrolytic, or something else.

When our circuit calls for an electrolytic capacitor the equivalent series resistance (ESR) becomes relevant and we need to take it into account. The ESR is so predominant that in our calculations for the minimum capacitance to mitigate ripple we can ignore the capacitance and use the ESR only as it is the feature which dominates. [Dr Ali] goes into detail for both examples using ceramic capacitors and electrolytic capacitors. Armed with the minimum capacitance (in Farads) and maximum ESR (in Ohms) you can then go shopping to find a capacitor which meets the requirements.

If you’re interested in capacitors and capacitance you might enjoy reading about Measuring Capacitance Against Voltage and Getting A Handle On ESR With A Couple Of DIY Meters.

Beating The World Record For Fastest Flying Drone Once Again

January 18, 2026 by 3 Comments

The fun part about world records is that anyone can take a swing at breaking them, which is what [Luke Maximo Bell] has been doing with the drone speed record for the past years, along with other teams in a friendly competition. After having some Aussie blokes previously smash the record with a blistering 626 km/h, the challenge was on for [Luke] and his dad to reclaim the title. This they did with the V4 of their quadcopter design, adding a range of improvements including new engines, new props and an optimized body to eek out more performance.

In the video we see these changes and the tests in detail. Interestingly, the simulations ran on the computer showed that the new body actually had to be larger, necessitating the use of a larger FDM printer. Fortunately a certain FDM 3D printer company sponsors just about everyone out there, hence the new design was printed on a Bambu Lab H2D, also making use of the dual extruder feature to print combined PETG/TPU parts.

It was also attempted to have a follow camera attached to a second FPV done in the form of a 360 degrees camera, but this turned out to be a bit too complex to get good shots, so this will have to be retried again.

In the end a new world record was set at an average of 657 km/h, which sets the stage for the next team to try and overtake it again. As for where the limit is, propeller airplanes have hit over 800 km/h,  so there’s still quite a way to go before details like the sound barrier become a problem.

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A Petabyte NAS Using Consumer-Grade Parts

January 17, 2026 by 4 Comments

Self-hosting a few services on one’s own hardware is a great way to wrest some control over your online presence while learning a lot about computers, software, and networking. A common entry point is using an old computer or Raspberry Pi to get something like a small NAS, DNS-level adblocker, or home automation service online, but the hobby can quickly snowball to server-grade hardware in huge racks. [Dennis] is well beyond this point, with a rack-mounted NAS already up and running. This build expands his existing NAS to one which can host a petabyte of storage out of consumer-grade components.

The main reason for building this without relying too much on server-grade gear is that servers are generally designed to run in their own purpose-built rooms away from humans, and as a result don’t generally take much consideration for how loud that environment becomes. [Dennis] is building a lot of the components from scratch for this build including the case, the backplanes for the drives, and a backplane tester. With backplanes installed it’s time to hook up all of the data connections thanks to a few SAS expanders which provide all of the SATA connections for the 45 drives.

There are two power supplies here as well, although unlike a server solution these aren’t redundant and each only serves half the drives. This does keep it running quieter, along with a series of Noctua fans that cool the rest of the rack. The build finishes off with an LED strip which provides a quick visual status check for each of the drives in the bay. With that it’s ready for drives and to be connected to the network. It’s a ton of wiring and soldering, and great if you don’t want to use noisy server hardware. And, if you don’t need this much space or power, we’ve seen some NAS builds that are a bit on the smaller side as well.

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The Shelly 2.5 Smart Relay Design Flaw Killing Capacitors

January 17, 2026 by 12 Comments

Part of any self-respecting Smart Home, smart relays are useful for switching and monitoring loads that do not plug into an outlet. This also makes them a lot more integrated, and thus, a long lifespan is very welcome. Unfortunately, the popular Shelly 2.5 smart relays seem to be having a bit of a design flaw as they’re dying in droves once their 2-year warranty period is up. The cause and repair are covered in a recent [VoltLog] video on YouTube.

As noted in the Shelly documentation for the device, it’s a very compact form factor device, with screw terminals, two relays, and three fairly large electrolytic capacitors sharing very little space with the rest of the components. The apparent flaw comes in the form of these capacitors failing, with the video showing that one 100 µF capacitor has a massively increased ESR, likely due to electrolyte venting. This results in the observed symptoms, such as WiFi connectivity issues and audible hissing, the latter of which is demonstrated in the video.

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A photo of the cats and the generated image

The Cutest Weather Forecast On E-Ink And ESP32

January 17, 2026 by 4 Comments

There’s a famous book that starts: “It is a truth universally acknowledged that a man in possession of a good e-ink display, must be in want of a weather station.” — or something like that, anyway. We’re not English majors. We are, however, major fans of this feline-based e-ink weather display by [Jesse Ward-Bond]. It’s got everything: e-ink, cats, and AI.

The generated image needs a little massaging to look nice on the Spectra6 e-ink display.

AI? Well, it might seem a bit gratuitous for a simple weather display, but [Jesse] wanted something a little more personalized and dynamic than just icons. With that in the design brief, he turned to Google’s Nano Banana API, feeding it the forecast and a description of his cats to automatically generate a cute scene to match the day’s weather.

That turned out to not be enough variety for the old monkey brain, so the superiority of silicon — specifically Gemini–was called upon to write unique daily prompts for Nano Banana using a random style from a list presumably generated by TinyLlama running on a C64. Okay, no, [Jesse] wrote the prompt for Gemini himself. It can’t be LLM’s all the way down, after all. Gemini is also picking the foreground, background, and activity the cats will be doing for maximum neophilia.

Aside from the parts that are obviously on Google servers, this is all integrated in [Jesse]’s Home Assistant server. That server stores the generated image until the ESP32 fetches it. He’s using a reTerminal board from SeedStudio that includes an ESP32-S3 and a Spectrum6 coloor e-ink display. That display leaves something to be desired in coloration, so on top of dithering the image to match the palette of the display, he’s also got a bit of color-correction in place to make it really pop.

If you’re interested in replicating this feline forecast, [Jesse] has shared the code on GitHub, but it comes with a warning: cuteness isn’t free. That is to say, the tokens for the API calls to generate these images aren’t free; [Jesse] estimates that when the sign-up bonus is used up, it should cost about fourteen cents a pop at current rates. Worth it? That’s a personal choice. Some might prefer saving their pennies and checking the forecast on something more physical, while others might prefer the retro touch only a CRT can provide. 

The Journey Of Finding The Right Press Brake

January 17, 2026 by 6 Comments

Press brakes are invaluable tools when working with sheet metal, but along with their almost infinite versatility comes a dizzying number of press brake types. After starting with an old-school, purely mechanical press brake, [Wes] of Watch Wes Work fame had been thinking of upgrading said press brake to a hydraulic configuration, but soured on this after facing all the disadvantages of the chosen approach. Thus, one does what any rational person does and purchases a used and very much untested 45-ton computer-controlled hydraulic press brake.

The video first explores the pros and cons of the various types of press brakes, with the issue of providing a balanced force across the entirety of the press brake’s dies being the largest problem. Although various mechanical and hydraulic solutions were attempted over the decades, a computer-controlled press brake like this Gasparini PBS 045 that [Wes] got is probably one of the more effective solutions, even if it provides the headache of more electrical and electronic things that can go wrong. The above screenshot of its basic workings should make that quite obvious, along with [Wes]’s detailed explanation.

As it turned out, this about 25-year-old Italian press brake wasn’t in such a terrible nick, but needed some badly needed TLC and obligatory breaker testing to bring it back to life. While it doesn’t like you not centering the part, this can be worked around by specifying that the part is actually larger than it is. Although [Wes] got it working well enough to do some work with it, it still has some gremlins left in it that will hopefully be hunted down over the coming time and video(s).

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The Best Robot Mop System: Flat, Spinning, Or Roller?

January 17, 2026 by 4 Comments

When it comes to designing a mopping robot, there are a number of approaches you can pick from, including just having the movement of the robot push the soggy mop over the floor, having spinning pads, or even a big spinning roller. But what difference does it make? Recently the [Vacuum Wars] channel ran a comparison to find out the answer.

The two spinning pad design is interesting, because it allows for the bot to move closer to objects or walls, and the base station doesn’t need the active scrubber that the simple static pad requires. The weakness of both types of flat mop design is that they are quickly saturated with dirt and moisture, after which they’ll happily smear it over the floor.

The spinning roller is the most complex, with the robot having its own onboard water tank, and a way to extract the dirty water from the mop and store it for disposal in the base station. Theoretically this would be the clear winner, with basically all of them having features like avoiding carpet.

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